Antistatic coating compositions

ABSTRACT

AN ANTISTATIC COATING FOR A POLYESTER FILM SUPPORT IS PROVIDED COMPRISING A HOMOGENEOUS MIXTURE OF (A) A CHLORINE-CONTAINING POLYMER CONSISTING OF AT LEAST 70% BY WEIGHT OF AT LEAST ONE MONOMER TAKEN FROM VINYLCHLORIDE AND VINYLIDENE CHLORIDE, AND (B) A POLYMERIC MATERIAL HAVING ELECTROCONDUCTIVE PROPERTIES, THE RATIO OF CHLORINE-CONTAINING POLYMER TO ELECTROCONDUCTIVE POLYMERIC MATERIAL VARYING BETWEEN 2:1 AND 1:2 PARTS BY WEIGHT.

United States Patent US. Cl. 252-500 6 Claims ABSTRACT OF THE DISCLOSUREAn antistatic coating for a polyester film support is providedcomprising a homogeneous mixture of (A) a chlorine-containing polymerconsisting of at least 70% by Weight of at least one monomer taken fromvinylchloride and vinylidene chloride, and (B) a polymeric materialhaving electroconductive properties, the ratio of chlorine-containingpolymer to electroconductive polymeric material varying between 2:1 and1:2 parts by weight.

This invention relates to antistatic coating compositions and tophotographic films and materials comprising them.

It is known that in photographic materials the usual synthetic filmsupports have the property of being charged electrostatically, so thatthe charged films strongly attract the surrounding dust and therebybecome soiled at their surface. Moreover, when such film supports areprovided with a silver halide emulsion layer, discharge images maybecome visible in the light-sensitive layer upon development. Such anelectrostatic charging results from the friction of the film support orlight-sensitive photographic material during winding or unwinding in thecoating, cutting or packing machines and by running the photographicmaterial through the camera ad the projector.

Although it is known that in practice the appearance of electrostaticcharges on synthetic resin supports can be avoided by the applicationthereto of an electroconductive layer, it is also known that in the caseof a polyester film support it is very difiicult to establish andmaintain a satisfactory bond between the surface of the polyester filmsupport and the antistatic layer applied thereto. In most cases morethan one layer is needed, for example first a special adhesive layerfollowed by the proper antistatic layer, whereto sometimes a protectivelayer is applied.

According to the invention a monolayer antistatic coating composition isprovided on a polyester film support, comprising an homogeneous mixtureof (A) a chlo fine-containing polymer consisting of at least 70% byweight of at least one monomer taken from vinyl chloride and vinylidenechloride, and (B) a polymeric material having electroconductiveproperties, the ratio of chlorine-containing polymer toelectroconductive polymeric material in said homogeneous mixture varyingbetween 2:1 and 1:2 parts by Weight.

The antistatic layer according to the invention makes that the polyesterfilm in photographic and other applications attracts no dust and causesno spark discharge any longer. This layer adheres to the polyester filmvery firmly, is very clear and is little susceptible to being scratched.If desired, the friction coefficient of this layer can still be loweredby the addition of a small amount of a suitable Wax.

The coating mixture of the antistatic layer comprises achlorine-containing polymer wherein at least 70% by weight of at leastone of the monomers taken from vinyl 3,786,002 Patented Jan. 15, 1974chloride and vinylidene chloride is present. Suitable polymers are e.g.:

after-chlorinated polyvinyl chloride,

the copolymer of vinyl chloride and vinyl acetate (85:15),

the copolymer of vinyl chloride and vinyl isobutyl ether the copolymerof vinylidene chloride and acrylonitrile the copolymer of vinylidenechloride, N-tert.-butylacry1- amide, n-butyl acrylate, andN-vinylpyrrolidone (70:23:324),

the copolymer of vinylidene chloride, N-tert.-butylacrylamide, n-butylacrylate, and itaconic acid (70:21:5:4),

the copolymer of vinylidene chloride, N-tert.-butylacrylamide, anditaconic acid (88:10:2),

the copolymer of vinylidene chloride, n-butylrnaleimide,

and itaconic acid (90:8:2),

the copolymer of vinyl chloride, vinylidene chloride, and

methacrylic acid (65: 30:5)

the copolymer of vinylidene chloride, vinyl chloride, and

itaconic acid (70:26:4),

the copolymer of vinyl chloride, n-butyl acrylate, and

itaconic acid (72:24:4),

the copolymer of vinylidene chloride, n-butyl acrylate and itaconic acid18:2),

the copolymer of vinylidene chloride, methyl acrylate,

and itaconic acid (:8:2),

the copolymer of vinyl chloride, vinylidene chloride, N-

tert.-butylacrylamide, and itaconic acid (50:30:18z2),

the copolymer of vinylidene chloride, methyl acrylate and itaconic acid(83zl5z2), and

the copolymer of vinylidene chloride, acrylonitrile and acrylic acid(78:12:10).

All the ratios given between brackets in the abovementioned copolymersare ratios by weight.

The above copolymers are only examples of the combinations that can bemade with different monomers, and the invention is not limited at all tothe copolymers enumerated.

The dilterent monomers indicated above may be copolymerized according tovarious methods. For example the copolymerization may be conducted in anaqueous dispersion containing a catalyst and an activator.Alternatively, polymerization of the monomeric components may occur inbulk without added diluent, or the monomers, may be allowed to react inappropriate organic solvent reaction media.

The coating mixture comprises also an electroconductive polymericmaterial to be chosen from a very large number of known polymers orcopolymers such as: polyethylene oxide, alkali metal salts of:

partially or completely sulphonated polystyrene (also in free acidform), copolymers of acrylic, methacrylic or maleic acid,polyvinylsulphonic acid (also in free acid form), polyvinylphosphonicacid, polyethylenimine hydrochloride, quaternized polyethylenimine,polymers and copolymers of:

N-vinyl-4-methyl-2-oxazolidinone, N-vinyltrimethylammonium chloride, N-3-acrylamido-propyl) -trimethylammonium chloride,acryloyloxyethyldimethylsulphonium chloride,N-(methacryloyloxyethyl)-trimethylammonium chloride,N-(methacryloyloxyethyl)-trimethylammonium methyl sulphate,N-(Z-hydroxy-3-methacryloyloxypropyl)-trimethylammonium chloride,

N-(acryloyloxyethyl)-pyridinium chloride, N-methyl-4-vinylpyridiniumchloride, vinylbenzyltrimethylammonium chloride,glycidyltributylphosphonium chloride, polymers obtained whenpolyepichlorohydrin is used as quaternizing agent for a tertiary amine,a tertiary phosphine or a secondary sulphide, polymers obtained by thereaction of polyepichlorohydrin with a secondary amine, e.g. morpholineor with a mercaptan such as Z-mercapto-ethanol, followed by thequaternization with an alkylating agent such as an ester of an alcoholand a strong acid such as the methyl or ethyl ester of sulphuric acid,phosphoric acid, hydrochloric acid, hydrobromic acid or hydroiodic acid,e.g. dimethyl sulphate or bromoethanol.

In order to form the antistatic layer on the polyester film support thechlorine-containing polymer and the electro-conductive polymericmaterial are dissolved in a common solvent or in miscible solvents. Theratio between both polymers naturally depends on the respective polymersused. In general a ratio taken between 1:2 and 2:1 ofchlorine-containing polymer to electroconductive polymeric material willgive good results as antistatic layer.

In order that the layer should have a sufficient conductivity and thatit can be used as an antistatic coating on a polyester film, the surfaceresistance should not exceed well defined limits, which themselves areinfluenced by the degree of relative humidity. For example, the surfaceresistance at 30% relative humidity should be lower than 1.10 ohm/ 10sq. cm., whereas at 60% relative humidity it should be lower than 1.10ohms/l sq. cm.

The antistatic coating composition is applied in such concentration andmanner known in the art as to yield on the polyester film support anantistatic layer having a thickness of preferably between 0.4 and 1.0micron.

The electroconductivity of the antistatic layer formed from the mixtureof chlorine-containing polymer and electroconductive polymeric materialis determined by measuring its surface resistance. Therefore, afterconditioning at a specific relative humidity a material composed of apolyester film support whereupon an antistatic coating according to theinvention is applied, the surface resistance of the material is measuredby means of a cell, both poles of which have a width of 0.5 cm. and areat a distance of 1 cm. from each other.

In the examples various layers and their conductivity are described.

In addition to the chlorine-containing polymer and the electroconductivepolymeric material the composition of the antistatic layer may includesmall amounts, e.g. between 10 and 20% by weight with respect to the dryweight of the whole coating composition, of a waxy material, such asunbranched saturated fatty acids, e.g. stearic acid and palmitic acid,esters derived from fatty acids and fatty alcohols, e.g. stearylstearate and n-hexadecyl palmitate, pentaerythritol esters of fattyacids such as stearic acid, palmitic acid and lauric acid, sucrosediesters of fatty acids such as sucrose distearate,N,N-alkylenebis-fatty acid amides, e.g. N,N-ethylene-bis-oleylamide andmontan wax derivatives, which are generally glycerol, glycol orpolymerized ethylene glycol esters of acids from montan wax. These waxymaterials are added to the coating composition of the antistatic layerto improve its resistance to friction and scratching.

The layer according to this invention may be applied by spray, brush,roller, doctor blade, air brush or wiping techniques. Due to thepresence of the chlorine-containing polymer the adherence of this layerto the polyester support is excellent in dry as well as in wet state.

According to the invention also a photographic film material is providedcomprising a polyester support, at least one light-sensitive silverhalide emulsion layer on one side of the polyester support, and anantistatic layer comprising the mixture of chlorine-containing polymerand of electroconductive polymeric material on the other side of thatsupport.

Films having an antistatic layer according to the present invention mayserve for the manufacture of photographic black-and-white as well ascolor films.

The monolayer antistatic coating can also be applied to both sides of apolyester film support. In this way a material is obtained that does notattract the surrounding dust, that has excellent optical properties andcan be used as a mounting foil, a drafting foil or as a support forcopying processes.

The examples given hereinafter especially refer to the use ofpolyethylene terephthalate film as support. The invention is notrestricted, however, to the use of film derived from thepolycondensation of terephthalic acid and ethylene glycol. In thepreparation of the high molecular weight polyester other glycols maypartially or wholly replace ethylene glycol, e.g. neopentyl glycol andl,4-di(hydroxymethyl)-cyclohexane. Terephthalic acid too may be replacedpartially or wholly by other dibasic acids such as, e.g., isophthalicacid, sebacic acid and adipic acid.

The following examples illustrate the present invention.

EXAMPLES l-6 6 portions were made of solutions of 0.6 g. of the sodiumsalt of copoly(styrene maleic acid) in 20 ml. of methanol and eachportion was mixed with ml. of butanone in which 0.3 g. of achlorine-containing polymer was dissolved. The differentchlorine-containing polymers were the following in the respectiveexamples:

The solution obtained was coated at a rate of 10 ml./ sq. m. on abiaxially oriented polyethylene terephthalate film of thickness. I

The layers applied were dried by evaporation of the solvents, andsamples of the coated films were conditioned at relative humidities of30 and 60%, whereafter their surface resistance was measured.Comparative tests were also made wherein the coating applied to thepolyester did not contain the electroconductive polymer. The followingresuts were noted.

Surface resistance in 10 ohm/10 sq.cm. at

30% rela- 60% relative hutive hu- Example number midity nudity For thesamples without electroconductive polymer surface resistances above500:10 ohm/sq. cm. were found.

In order to improve the resistance of the antistatic layer to frictionand scratching a small amount of a Waxy material such asN,N-ethylene-bis-stearamide, for instance between 10 and 20% by Weightwith respect to the dry weight of the antistatic layer, was added to thecoating composition. This small amount did not harm the surfaceresistance.

EXAMPLES 7-9 In the examples the surface resistance of polyester filmmaterials coated with an antistatic layer was measured with varyingratio of electroconductive polymer in the antistatic layer.

Three portions of 0.6 g. of copolymer of vinylidene chloride,N-tert.-butyacrylamide, n-butyl acrylate and N- vinylpyrrolidone(70:23:3:4% by weight) were dissolved each in 80 ml. of butanone.

To each solution a quantity of the sodium salt of the copolymer ofstyrene and maleic acid was added dissolved in 20 ml. of methanol. Thesequantities were as follows:

In Example 7: 0.3 g. In Example 8: 0.45 g. In Example 9: 0.6 g.

The solutions were coated on a biaxially oriented polyethyleneterephthalate film of 180g. After evaporation of the solvents, thesurface resistance of the different samples was measured at 30 and 60%of relative humidity. The following results were noted.

Surface resistance in 10 ohm/10 sqmn. at-

30% rela- 60% relative hutive hu- Example number midity nudity EXAMPLES10-13 In these examples the surface resistance of polyester filmmaterials coated with an antistatic layer was measured wherein theantistatic layer contained different electroconductive polymers.

Four portions of 0.3 g. of copolymer of vinylidene chloride,N-tert.-butylacrylamide, n-butyl acrylate and N- vinylpyrrolidone(70:23:3:4% by weight) were dissolved each in a mixture of 50 ml. ofbutanone and 10 ml. of ethylenechlorohydrin. Each time an amount of 0.6g. of electroconductive polymer was dissolved in 40 ml. of butanone andadded to the chlorine-containing polymer solutions. Theelectroconductive polymers used were the following:

The solutions were coated on a biaxially oriented polyethyleneterephthalate film of 100g. The solvents were evaporated and the surfaceresistance of the different samples was measured at 30 and 60% ofrelative humidity. The following results were obtained:

Surface resistance in 10 ohm/10 sq.em. at-

30% rela- 60% relative hutive hu- Example number midity midity EXAMPLE14 0.5 g. of the copolymer of styrene and styrene sulphonic acid (77:23mole percent) was dissolved in a mixture of 20 ml. of methanol and 5 ml.of ethylenechlorohydrin. To this solution is added a solution of 0.3 g.of the copolymer of vinyl chloride and vinyl acetate (87:13% by weight)in 75 ml. of butanone.

The solution was applied to a biaxially oriented polyethyleneterephthalate film of 180 and dried.

The surface resistance values of the coated polyester film were found tobe O.0l l0 ohm/l0 sq. cm. and 0.0001 10 ohm/l0 sq. cm. at 30% and 60%relative humidity respectively.

EXAMPLE 15 0.5 g. of the copolymer of N-(methacryloyloxyethyl)trimethylammonium methylsulphate, ,B-chloroethyl acrylate and acrylicacid (60:25:15) mole percent) was dissolved in 20 ml. of methanol, andthis solution was mixed with 0.3 g. of the copolymer of vinyl chlorideand vinyl acetate (87:13% by weight) dissolved in ml. of butanone.

The solution was applied to a biaxially oriented polyethyleneterephthalate film of p. and dried.

The surface resistance of the coated polyester film was found to be 0.3l0 ohm/ 10 sq. cm. and 0.005 10 ohm sq. cm. at 30% and 60% of relativehumidity respectively.

EXAMPLE 16 The front side of a biaxially oriented polyethyleneterephthalate film having a thickness of 63;]. was coated with thefollowing composition at 2530 C. at a rate of 1.5 to 1.75 g./sq. m.:

'Copolymer of vinylidene chloride, N-tert.-butylacrylamide, n-butylacrylate and N-vinylpyrrolidone (70:23:3:4% by weight) g 5.5 Methylenechloride ml 65 1,2-dichloroethane ml 35 The copolymer was manufacturedaccording to the process described in Example 1 of Belgian patentspecification 721,469, filed Sept. 27, 1968 by Gevaert-Agfa N.V.

After drying of the layer, a second layer was applied thereto in aproportion of 25 ml./sq. m. from the following composition:

20% latex of copolymer of butadiene and methyl methacrylate (50:50% byweight) ml 60 10% aqueous solution of gelatin ml 80 Water ml 457.5Silica g 5 Methanol ml 400 10% aqueous solution of a surface activecoating aid ml 2.5

The latex was manufactured according to the process described in Example1 of Belgian patent specification 721,469 mentioned above.

After drying, a light-sensitive gelatin silver halide emulsion layer wasapplied to the latter layer, said emulsion being manufactured asfollows:

A solution of 100 g. of silver nitrate in 1 litre of water was added at47 C. in a period of time of 30 sec. to a solution of 70 g. of potassiumbromide, 1 g. of potassium iodide and 25 g. of gelatin in 500 ml. ofwater.

10 min. later 70 g. of gelatin were added, and after 30 min. theemulsion was solidified. Thereupon the emulsion was shredded, rinsed for5 min., admixed with 40 g. of ripening gelatin, and maintained at 50 C.for 4 min. The fine-grained emulsion thus obtained was coated so thateach sq. m. carried an amount of silver halide equivalent to 4 g. ofsilver.

The rear side of the polyethylene terephthalate film support wasprovided with an antistatic layer at 10 ml./ sq. m. from a coatingcomposition consisting of:

Copolymer of vinyl chloride and vinyl acetate ('87:13% by weight) g 30Copolymer of styrene and maleic acid sodium salt (50:50) g 50N,N-ethylene-bis-oleylamide g 12 Butanone ml 750 Methanol ml 200Ethylene chlorohydrin ml 50 The antistatic properties of thisphotographic material were very good. The surface resistance measured onthe rear side amounted to O.5 l ohm/ 10 sq. cm. at 30% relativehumidity. Dust was not attracted by this film. After storage in rollform it appeared that the photographic properties of the emulsion, whichhad been in contact with this rear side, had not been impaired.

EXAMPLE 17 To the front side of a biaxially oriented polyethyleneterephthalate film having a thickness of 180 a layer was applied at arate of 1.4 g./sq. m. from the following composition:

Copolymer of vinylidene chloride, N-tert.-butylacrylamide, n-butylacrylate and N-vinylpyrrolidone (70:23:3:4% by weight) g Methylenechloride ml 60 1,2-dichloroethane ml 35 Methanol ml 5 After drying thislayer, the surface thereof was exposed to 4 successive corona dischargesfrom a high frequency power supply. This power supply produced apulsating voltage, the waveform comprising a narrow pulse of a magnitudeof 500 kv., followed by a flat portion of 5 kv. The repeat frequencyamounted to about 35 kc. The current intensity for each electrode was1.5 X a./cm. and the film speed was 10 m./min.

After the corona discharge treatment a light-sensitive gelatin silverhalide emulsion layer as described in Example 16 was applied.

The rear side of the polyethylene terephthalate film support wasprovided with an antistatic layer as described in Example 16, exceptthat as antistatic polymer 2. copolymer of styrene, sodium maleate andfl-chloroethyl 8 acrylate (45/45/10) was used. On drying of the layerthis antistatic copolymer became insoluble as described in our copendingUnited Kingdom patent application 4,946/ 69, filed Jan. 29, 1969 byGevaert-Agfa N.V. (title: Electroconductive Layers).

The antistatic properties of the photographic material before as well asafter treatment in the photographic baths was excellent.

We claim:

1. An antistatic coating composition for a polyester film support,comprising an homogeneous mixture of (A) a chlorine-containing polymerconsisting of at least 70% by weight of at least one monomer taken fromvinyl chloride and vinylidene chloride, (B) a polymeric material havingelectroconductive properties, and (C) about 10 to 20%. by weight of awaxy material, the ratio of chlorine-containing polymer toelectroconductive polymeric material in said homogeneous mixture varyingbetween 2:1 and 1:2 parts by weight, said composition having a surfaceresistance at 30% RH of less than 1.10 ohm/10 sq. cm. and at RH lessthan 1.10 ohm/ 10 sq. cm.

2. An antistatic coating composition according to claim 1, wherein thechlorine-containing polymer is a copolymer of vinyl chloride and vinylacetate containing 87% by weight of vinyl chloride.

3. An antistatic coating composition according to claim 1, wherein thechlorine-containing polymer is the copolymer of vinylidene chloride,N-tert.-butylacrylamide, n-butyl acrylate and itaconic acid (:23:3:4% byweight).

4. An antistatic coating composition according to claim 1, wherein thepolymeric material having electroconductive properties is the sodiumsalt of the copolymer of styrene and maleic acid (50:50 mole percent).

5. An antistatic coating composition according to claim -1, wherein thepolymeric material having electroconductive properties is the sodiumsalt of the copolymer of N- (methacryloyloxyethyl)-trimethylammoniummethylsulphate, B-chloroethyl acrylate and acrylic acid (60:25:15 molepercent).

6. An antistatic coating composition according to claim 1, vgherein thewaxy material is N,N-ethylene-bis-oley1- arm e.

References Cited UNITED STATES PATENTS 2,627,088 2/ 1953 Alles et al.9687 A 3,514,291 5/1970 Vanpoecke et al. 9687 A 3,632,526 1/1972Yamamoto et al. 252500 3,563,921 2/1971 Bourat 117-2101 RONALD H. SMITH,Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 ,786,002Dated January 15, 1974 Inventor(s) August Jean VAN PAESSCHEN et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the heading of the patent, correct the assignee '5 name from "AgfaN.V." to Agfa-Gevaert N.V.

Signed and sealed this 21st day of May 1971p.

SEAL Atte'st:

EDWARD M .1" LET CHER JR G 1m: SHALL DAN 1; Attesting Officer Cammissioner of Patents USCOMM-DC 60376-P69

